This invention relates to the production of phenol and more particularly to a process for producing phenol and acetone from cumene hydroperoxide.
Phenol is an important organic chemical with a wide variety of industrial uses. It is used, for example, in the production of phenolic resins, bisphenol-A and caprolactam. A number of processes are currently in use for the production of phenol but the process providing the largest proportion of the total production capacity is the cumene process which now accounts for over three quarters of the total U.S. production. The basic reaction involved in this process is the cleavage of cumene hydroperoxide into phenol and acetone:
C6H5C(CH3)2OOHxe2x86x92C6H5OH+(CH3)2CO
On the industrial scale, the cumene hydroperoxide is usually treated with dilute sulphuric acid (5 to 25 percent concentration) at a temperature of about 50xc2x0 C. to 70xc2x0 C. After the cleavage is complete, the reaction mixture is separated and the oil layer distilled to obtain phenol and acetone together with cumene, alpha-methylstyrene, acetophenone and tars. The cumene may be recycled for conversion to the hydroperoxide and subsequent cleavage. The phenol produced in this way is suitable for use in resins although further purification is required for pharmaceutical grade product.
Although the process described above is capable of producing both phenol and acetone in good yields, it would be desirable to find a process that would reduce the need for the product separation and purification steps inherent in a homogeneous process and that would avoid the need for environmentally hazardous liquid acid catalysts.
The heterogeneous cleavage of cumene hydroperoxide (CHP) over various solid acid catalysts has already been reported. For example, U.S. Pat. No. 4,490,565 discloses the use of zeolite beta in the cleavage of cumene hydroperoxide, whereas U.S. Pat. No. 4,490,566 discloses the use of a Constraint Index 1-12 zeolite, such as ZSM-5, in the same process.
In addition, U.S. Pat. Nos. 6,169,215 and 6,169,216 disclose cumene hydroperoxide cleavage over solid acid catalysts formed by modifying a Group IVB metal oxide with a Group VIB metal oxyanion and by sulfating transition metal oxides.
Solid acid catalysts having sulfonic acid groups have also been proposed for use in cumene hydroperoxide cleavage. For example, U.S. Pat. No. 4,898,995 discloses a process for the coproduction of phenol and acetone by reacting cumene hydroperoxide over a heterogeneous catalyst comprising an ion exchange resin with sulfonic acid functionality. In such a catalyst the sulfonic acid functional group is bonded to an organic, preferable polystyrene or styrene-divinylbenzene, polymer backbone. Given the organic nature of this support, these catalysts are sensitive to temperature, and typically cannot be used above
In addition, the article entitled xe2x80x9cDecomposition of Cumyl Hydroperoxide in the presence of Sulfonated Silica in a Flow-Type Systemxe2x80x9d, from Neftekhimiya, 33, No. 1, 41-45, 1993 discloses cumene hydroperoxide cleavage over a catalyst obtained by modifying amorphous silica with a chlorosilane and then treating the modified silica with chlorosulfonic acid. However, as discussed in more detail below, tests with amorphous silica catalysts having sulfonic acid functionality have shown the catalysts to have only limited activity for the cleavage reaction.
Accordingly, there is an ongoing need for a solid-acid cumene hydroperoxide cleavage catalyst that exhibits the required combination of activity and selectivity to provide an acceptable replacement for sulfuric acid catalysts.
The present invention is directed to a process for producing phenol and acetone from cumene hydroperoxide, wherein the process comprises the step of contacting cumene hydroperoxide with a solid-acid catalyst comprising an inorganic, porous, crystalline material, designated as M41S, exhibiting, after calcination, an x-ray diffraction pattern with at least one peak at a d-spacing greater than about 18 Angstrom Units with a relative intensity of 100 and a benzene adsorption capacity of greater than 15 grams of benzene per 100 grams of said material at 50 torr and 25xc2x0 C., wherein said material comprises sulfonate functionality.
The process of the invention achieves enhanced conversion of cumene hydroperoxide to phenol and acetone. Although the reason for this improvement is not fully understood, it is believed that the exceptionally high surface area of the M41S type materials allows for correspondingly high numbers of sulfonic acid groups and hence for an enhanced acid activity.
Preferably, the porous, crystalline material has uniform pores within the range of from about 13 Angstroms to about 200 Angstroms, more usually from about 15 Angstroms to about 100 Angstroms.
Preferably, the porous, crystalline material has, after calcination, a hexagonal arrangement of uniformly-sized pores having diameter of at least about 15 Angstrom Units and exhibits a hexagonal electron diffraction pattern that can be indexed with a d100 value greater than about 18 Angstrom Units.
Preferably, the porous crystalline material is a silicate or aluminosilicate.
Preferably, said contacting step is conducted at a temperature of 20xc2x0 C. to 150xc2x0 C. and a pressure of atmospheric to 1000 psig (100 to 7000 kPa) and more preferably at a temperature of 40xc2x0 C. to 120xc2x0 C. and a pressure of atmospheric to 400 psig (100 to 2860 kPa).
The present invention provides an improved process for producing phenol and acetone from cumene hydroperoxide, wherein the process comprises the step of contacting cumene hydroperoxide with a solid-acid catalyst comprising an inorganic, porous, crystalline material, designated as M41S, exhibiting, after calcination, an x-ray diffraction pattern with at least one peak at a d-spacing greater than about 18 Angstrom Units with a relative intensity of 100 and a benzene adsorption capacity of greater than 15 grams of benzene per 100 grams of said material at 50 torr and 25xc2x0 C., wherein said material comprises sulfonate functionality.
M41S materials and their synthesis are described in U.S. Pat. No. 5,102,643, the entire contents of which are incorporated herein by reference. M41S materials are mesoporous and for use herein preferably have uniform pores within the range of from about 13 Angstroms to about 200 Angstroms, more usually from about 15 Angstroms to about 100 Angstroms. Control of the pore size within the above range is conveniently achieved by the process described in U.S. Pat. No. 5,057,296, the entire contents of which are also incorporated herein by reference.
In their calcined form, M41S materials have the following composition:
Mn/q(WaXbYcZdOh)
wherein W is a divalent element, such as a divalent first row transition metal, e.g. manganese, cobalt and iron, and/or magnesium, preferably cobalt; X is a trivalent element, such as aluminum, boron, iron and/or gallium, preferably aluminum; Y is a tetravalent element such as silicon and/or germanium, preferably silicon; Z is a pentavalent element, such as phosphorus; M is one or more ions, such as, for example, ammonium, Group IA, IIA and VIIB ions, usually hydrogen, sodium and/or fluoride ions; n is the charge of the composition excluding M expressed as oxides; q is the weighted molar average valence of M; n/q is the number of moles or mole fraction of M; a, b, c, and d are mole fractions of W, X, Y and Z, respectively; h is a number of from 1 to 2.5; and (a+b+c+d)=1. In a preferred embodiment, the porous crystalline material used herein has a composition wherein a and d=0, and h=2, namely the material is a silicate or metallosilicate, preferably an aluminosilicate.
A preferred form of the crystalline material for use in the process of the invention exhibits, after calcination, a hexagonal arrangement of uniformly-sized pores having diameter of at least about 15 Angstrom Units and exhibits a hexagonal electron diffraction pattern that can be indexed with a d100 value greater than about 18 Angstrom Unit. This material, identified as MCM-41, and its preparation and properties are described in further detail in U.S. Pat. No. 5,098,684, incorporated herein by reference.
Alternatively, the crystalline material used in the process of the invention can have the cubic arrangement of pores as described in U.S. Pat. No. 5,198,203 or the lamellar structure as described in U.S. Pat. No. 5,304,363, both of which patents are incorporated herein by reference.
In the solid acid catalyst used in the process of the invention, the porous crystalline material is functionalized by the introduction of sulfonyl groups. This can be achieved by any method known in the art for introducing sulfonate functionality. Such methods include (1) reacting mercaptans, sulfides, disulfides, sulfoxides or sulfones with oxidizing agents such as potassium permanganate, chromic anhydride, aqueous bromine, hydrogen peroxide and nitric acid, (2) reacting alkylhalides with sodium, potassium or ammonium sulfite in aqueous ethanol solution under refluxing conditions (the Strecker reactions), and (3) the addition of bisulfites to unsaturated compounds such as olefins in the presence of oxygen or other oxidizing agents to give the corresponding alkylsulfonic acid. For example, where the porous crystalline material is a silicate or metallosilicate, the material can be reacted with a mercaptoalkoxysilane, such as (3-mercaptopropyl)trimethoxysilane, and the resultant thiol groups bonded to the surface of the material can be oxidized to the desired sulfonyl groups with hydrogen peroxide.
The cleavage reaction of the invention is typically effected by contacting the cumene hydroperoxide with the solid acid catalyst described above in the liquid phase at a temperature of 20xc2x0 C. to 150xc2x0 C. and a pressure of atmospheric to 1000 psig (100 to 7000 kPa) and more preferably at a temperature of 40xc2x0 C. to 120xc2x0 C. and a pressure of atmospheric to 400 psig (100 to 2860 kPa). To effect the contacting of the cumene hydroperoxide, the solid acid catalyst described above may be contained in a stationary or fluidized bed, and the contacting operation may take place continuously or batch-wise. If the contacting takes place continuously, the liquid hourly space velocity (LHSV) based on cumene hydroperoxide is within the range of 0.1 to 100 hrxe2x88x921, preferably 1 to 50 hrxe2x88x921. If the contacting takes place batch-wise, the residence time is within the range of 1 to 360 min, preferably 1 to 180 min. The cumene hydroperoxide is preferably dissolved in an organic solvent inert to the cleavage reaction, such as benzene, toluene, acetone and most preferably acetone. The use of a solvent is preferred to assist in dissipating the heat of reaction (about 60 kcal/mol).
The invention will now be more particularly described with reference to the following Examples.